Patent Document 1 discloses a pressure distribution measurement sensor sheet having a sheet area where a plurality of rectangular electrodes are vertically aligned in a horizontal orientation, and another sheet area where a plurality of rectangular electrodes are horizontally aligned in a vertical orientation. A pressure-sensitive layer is provided on the electrodes of each of the two sheets. The two sheets are laminated in such a manner that the pressure-sensitive layer of each of the sheets contacts each other to constitute a pressure distribution measurement sensor sheet. In the sensor sheet, the rectangular electrodes arranged in each of the sheet areas intersect one another. Each of the intersections functions as a pressure-sensitive region to realize a pressure distribution sensor having a matrix structure. Pressure distribution measurement is possible in the sensor sheet by sequentially energizing the electrodes and measuring electric resistance between the electrodes.
The sensor sheet of Patent Document 1 is capable of properly measuring pressure distribution when disposed on a plane surface; however, when disposed on a flexible support such as mattress or futon mattress, the sensor sheet is not capable of deforming to conform to unevenness of a surface of the support. This prevents the sensor sheet from properly measuring pressure distribution. A conceivable approach to solving the problem is adopting a stretchable material such as vinyl chloride or ethyl carbonate as a substrate. Such a case requires wires formed by applying ink on the substrate to be stretched as well in accordance with the sensor sheet. Nonetheless, it is difficult to give stretchability to the sensor sheet while maintaining the electrical properties of the wires. Further, although the ink needs to be dry to cure when forming a wire, having stretchability makes it difficult for the ink to do so.
As a solution to the above problem, Patent Document 2 discloses a body pressure distribution sensor sheet having stretchability. In the sensor sheet, a plurality of electrodes having pressure-sensitive resistors laminated thereon are arranged apart from one another to form a matrix, and adjacent electrodes are connected by a wire. Further, around each of the electrodes on the sensor sheet is a spiral cut line formed without intersecting with the wire, enabling the entire sheet to stretch.
Patent Document 1: Tokukai 2004-333273 (Japanese Unexamined Patent Publication)
Patent Document 2: WO-A1-2005068961